Conventionally, there is known a configuration which allows attachment of a battery pack which can be directly attached to an electric tool and attachment of a battery pack different from the above battery pack by, e.g., Japanese Patent Application Publication No. 2008-73799 (hereinafter referred to as “Document 1”). In the electric tool of Document 1, placement of an electric tool adaptor between the electric tool and the battery pack allows a plurality of types of battery packs to be attached to the electric tool.
The electric tool adaptor of Document 1 allows the battery pack, which cannot be directly attached to the attachment portion of the electric tool due to a difference in shape, to be attached to the electric tool via the adaptor simply by configuring the shape of the adaptor such that the shape thereof fits the battery pack and the electric tool.
By connecting the electric tool and the battery pack with the electric tool adaptor having the above configuration disposed between the electric tool and the battery pack, it becomes possible to attach a plurality of types of battery packs to a specific electric tool.
By the way, if the above electric tool adaptor is used, even when the voltage of the battery pack is different from the rated voltage of the electric tool, a user can use the electric tool. However, the rated voltage indicates a voltage at which the electric tool can be safely used, and hence, when the battery pack having a voltage higher than the rated voltage is used, there have been chases where heat generated by a motor in the electric tool is increased and the electric tool breaks down. On the other hand, when the battery pack having a voltage lower than the rated voltage is used, there have been cases where performance required by the user cannot be exhibited.